Clamp for dental impression trays



April 6, 1943.

B. F. SAHR CLAMP FOR DENTAL IMPRESSION TRAYS Fil'ed Sept. 28, 1940 2Sheets-Sheet l BIYjd/ill April 6, 1943. s. F. SAHR CLAMP FOR DENTALIMPRESSION TRAYS Filed Sept. 28, 1940 2 Sheets-Sheet 2 0 xx 12 0 fPatented Apr. 6, 1943 UNITED STATES PATENT OFFICE CLAMP FOR DENTALIMPRESSION TRAYS Benjamin F. Sahr, gHu'tchinson, Minn.

Application September 28, 1940, Serial No. 358,799

8 Claims.

This invention relates to the dental art. In this art in making the moldimpression of the lower denture the impression material is contained ina tray. Such a tray is disclosed and claimed in my prior Patent No.1,629,177 of May 17, 1927, and in the use of such a tray it is of theutmost importance not only that the pressure on the two sides of thetray be equalized, but that, while the setting of the material in thetray is taking place the tray be held against the lower jaw underconstant and unvarying pressure.

In the common practice of using both hands to apply pressure to hold thetray in position, it is known that a muscle movement or twitching existsin the hands and arms which reduces the chances for a successful andperfect impression.

It is also known that in the use of a pressure machine duplicating theacts of impression taking of the lower jaw, the dentist, if righthanded,

exerts unconsciously up to thirty per cent more pressure with his righthand than with his left hand and that the reverse is true if lefthanded. This unequal pressure is coupled with muscular twitching of bothhands in a two-handed technique,

Another fact of great importance is that resilient tissue covers thebony process of the lower law. This tissue can be compressed on applyingpressure to it, and being resilient it will spring back or resume itsnatural position when the pressure is taken away. This movement is veryslight, but very quickly lifts the denture from the ridge. Equalpressure must be applied to this resilient tissue in impression takingor the denture will not occlude perfectly with the tissue of the jaw. Ifthe denture does not occlude perfectly we cannot obtain vacuum, so tospeak, between the denture and tissue.

The present invention provides an extremely simple and highly efficientclamp for holding the impression tray against the lower jaw ridge orstress bearing area in the desired manner above indicated.

In the accompanying drawings, which illustrate the invention, likecharacters indicate like parts throughout the several views.

Referring to the drawings:

Fig. 1 is a perspective showing the tray and clamping device applied inuse, the outline of the human head being indicated by dotted lines; Fig.2 is a transverse section taken through the lower jaw and showing thetray and clamp in cross section;

ing shown in elevation;

Fig. 4 is a side elevation showing a modified form of the clamp;

Fig. 5 is a view in perspective corresponding to Fig. 1, butillustrating a somewhat modified structure;

Fig. 6 is a transverse section taken through the lower jaw and showingthe tray and clamping cross-section of the modified structureillustrated in Fig, 5; and

Fig. 7 is a side elevation of the clamp shown in Figs. 5 and 6.

Referring first to the preferred construction illustrated in Figs. 1, 2and 3, the U-shaped dental tray is indicated by the numeral 6. This trayis provided with a transverse pressure bar 7, which at its centralportion has a depression or pocket 8. In Fig. 2 the fleshy part of thelower jaw is indicated by the character a, the jaw bone by the characterI) and the tongue base by the character 0. In Fig. 2 this tray is shownas holding the molding plastic material 9 preferably positioned on thelower jaw.

The tray clamp, as preferably designed, involves a clamping frame thatis made from a narrow piece of flat metal, preferably aluminum, platedwith a non-corrosive material such as nickel, chromium or the like. Theframe may be roughly described as made up of an approximately U-shapedupper portion In and a reversely formed and smaller approximately U-shaped lower portion ll. These portions in and ll are, as shown,preferably bent approximately rectangular, but might vary considerablyfrom that rectangular form and could then be described also asapproximately C-shaped. The upper prong of the upper body portion H] hasa downturned bearing lug I2, the point of which is adapted to be seatedin the pocket 8 of the pressure bar I of the tray 6. Extended throughthe base of the upper portions 10 and II, in axial alignment with thepoint of the bearing lug I2, is a stem or rod I3, which at its upper endis provided with a clamping bar l4 that is preferably bent to fit theunder jaw and press against the fleshy portion immediately under the jawbone 1). The stem I3 is screw-threaded and working thereon is a nut I5,between which and the lower prong H is interposed a coiled spring It. Byadjustments of the nut IS on the stem I3 the clamping bar l4 may beraised and lowered and the tension of spring 16 may be varied. Thecharacter l5 indicates a nut that is screwthreaded on the extreme lowerend of stem l3 to limit the upward movement thereof. Preferably thedepending portion of frame I0 is graduated to indicate the amount ofpressure exerted by spring l6.

Applying the device as shown in Figs. 1 and 2, the bearing lug I2 islocated in the pocket 8 of the pressure bar I, and the nut 15 is screweddown on the stem it until the clamping bar M is pressed against thelower jaw with sufiicient force to properly seat the tray and hold theplastic material against the lower oral surface with exactly the rightpressure. The spring l6 produces a yielding or cushioning action betweenthe clamp id and the clamping frame, which is very desirable in mostinstances, but if very considerable pressure should be required the nutIE will be screwed down'until the spring it has been solidly compressed.In either event or even if the spring It should be omitted, the nut IEwill react against the lower portion of the clamping frame and willcause the plastic ma- I terial in the tray to be pressed down and reactagainst the lower denture stress bearing area of lower jaw surface.Obviously, when the clamp has been applied to hold the tray under thedesired pressure, the pressure will be equalized on both sides of thetray and there will be no shaking, vibrating or variation in the appliedpressure.

The device may be quickly applied, and while it is applied there is nonecessity whatever for application of the dentists hand in the oralcavity.

In Fig. l, I have shown a modified device in which the clamping frame Hais provided with a-stem or rod liia equipped at its upper end with apressure bar Ma between which and the base of the frame section Ilia isinterposed a coiled spring lta, the expansion of which is limited by akey or the like ll applied to the lower end of the stem. The use of thismodified device is evident.

Figs. 5, 6 and 7 illustrate an important further modification of theinvention in which the tray Ed has no bridge bar but has depressedcontact bosses 6b, one on each prong or side thereof. In this modifiedstructure many of the parts thereof are identical with or very similarto parts illustrated in Figs. 1 to 4, inclusive, and hence,

these parts will be designated by the same numerals with the exponentsI) applied thereto.

In this modified structure, however, the upper arm of the frame i isshorter than in the earlier described structure and to this short upperarm a pair of arms it are pivoted by a nut-equipped bolt [9. At theirfree ends the arms l8 are provided with contact screws 2i! that areengageable with the depressions of the bosses 6b on the tray 6a. Thearms [8 are adapted to be spread for proper engagement with theparticular tray and the screws 29 can be independently adjusted toobtain proper distance between the pressure bar or chin rest 14?) andthe points of said screws. By adjustments of the nut on the screwthreaded stem, the device may be adjusted so as to produce an evenpressure on the tray even when there is an uneven jaw recession.

It is important to note, in the several forms of the device abovedescribed, see particularly Figs. 1, and 7, that when either of the saiddevices is assembled and applied as illustrated and described, thechin-engaging clamp will be substantially in the same transversevertical plane as the point of contact between the tray and the trayengaging element on the upper prong of said frame. In the one case thestem i3 will be in the same transverse plane with the upper contactpoint I 2 and in the other case the axis of said stem will be in thesame transverse vertical plane that intersects the points of the screws20.

To adapt the device for application to exceptionally large chinformations, it may be desirable, in some instances, to make the socalledU-shaped frame vertically adjustable so as to increase or decrease thedistance between the chin-engaging clamp or bar and the tray. In Fig. 4,I have illustrated a means for accomplishing such vertical adjustmentand which means consists in dividing or making in sections the verticalportion of the frame [0a and providing one of the sections with verticalslots 2| and dividing the other section with screws 22, and which screwswork in the slots of the one section and have threaded engagement withthe other section. This same kind or similar vertical adjustment may beapplied to the other forms of the device illustrated.

These features just noted are of very great importance in maintainingthe clamp in good position and applying the pressure on the tray in avertical or downward direction.

From the foregoing it will be understood that the various othermodifications may be made within the scope of the invention hereindisclosed and claimed.

This case is being filed as a continuation-inpart of my copendingapplication Clamp for dental impression trays, filed May 16, 1938, underS. N. 208,239, and allowed April 4, 1940.

It will be noted that the chin-engaging clamp I4 is in the form of a barthat is substantially the same width as the U-shaped clamp and iscapable of being turned to a position parallel to the body of theU-shaped clamp thereby producing a substantially flat formation capableof being readily placed in an envelope or the like.

What I claim is:

1. A dental device comprising an impression tray, an approximatelyU-shaped clamping frame having upper and lower prongs and provided atits upper prong with means for detachable contact with said tray andprovided at its lower prong with an approximately reversely U- shapedminor portion, a chin-engaging clamping bar having a depending stem thatis freely movable endwise in said U-shaped minor portion, and a springapplied around said stem and reacting against said frame to yieldinglypress said stem and chin-engaging bar upward.

2. A dental device comprising an impression tray, an approximatelyU-shaped clamping frame having upper and lower prongs and prov1ded atits upper prong with means for detachable contact with said trayprovided at its lower prong with an approximately reversely U- shapedminor portion, a chin-engaging clamping bar having a depending stem thatis reely movable endwise and rotatively in said U-shaped minor portion,and a spring applied around said stem and reacting against said frame toyieldingly press said stem and chin-engaging bar upward.

3. The structure defined in claim 2 in which said stem is threaded andin further combination with a nut working on said threaded stem andoperative to vertically adjust said chin-engaging bar and stem and tovary the tension of said spring.

4. A dental device comprising an approximately U-shaped clamping framehaving upper and lower prongs and provided at its upper prong with meansfor detachable contact with a dental tray and provided at its lowerprong with an integral depending minor portion which is alsoapproximately U-shaped, a chin-engaging clamping bar having a dependingstem that is freely movable endwise and rotatable in said U-shaped lowerprong and minor portion, and a spring ap-- plied on said stem andreacting against the same and said frame with a force yieldinglypressing said chin-engaging bar and its stem upward, said chin-engagingclamping bar having approximately the same width as said clamping frameso that it may be turned on its mounting into a plane aligned with thebody of the frame.

5. The structure defined in claim 4 in which said stem is externallythreaded and in further combination with a nut applied on said threadedstem and operative to vertically adjust the latter and to vary thetension of said spring.

6. The structure defined in claim 1, in which the said stem is threaded,and in which the said spring is located in the minor U-shaped portion ofthe clamping frame and seats against the bottom thereof, and in furthercombination with a tension adjusting nut working on said threaded stemwithin the minor U-shaped portion and against the upper end of saidspring.

7. A dental device comprising an impression tray, an approximatelyU-shaped clamping frame having upper and lower prongs and provided atits upper prong with means for detachable contact with said tray, achin-engaging clamping bar having a depending stern that is freelymovable endwise through the lower prong of said frame, and a springapplied around said stem and reacting against said frame to vieldablypress the chin-engaging bar upwardly in sub stantial alignment with themeans for detachably contacting the tray.

8. The structure defined in claim '7 in which said stem is threaded andin further combination with a nut working on said threaded stem andoperative to adjust the tension of said spring.

BENJAMIN F. SAHR.

